Dating of recent sediments from Lago Maggiore and Lago di Lugano (Switzerland/Italy) using 137 Cs and 210 Pb.

This paper presents the results of ¹³⁷ Cs and ²¹⁰ Pb dating of sediments from the northern and western basins of Lago Maggiore and the southern basin of Lago di Lugano. Vertical distributions of ¹³⁷ Cs in sediment cores taken in 2017/18 were compared to those of the sediment cores taken almost two decades ago at the same positions. This comparison showed that ¹³⁷ Cs peaks do not alter their shape significantly over time and ¹³⁷ Cs remains a reliable time-marker for many decades. ²¹⁰ Pb dating using for the first time the piecewise "constant rate supply" (CRS _PW ) model constrained with ¹³⁷ Cs time-markers is performed for sediment cores of Lago Maggiore and Lago di Lugano. "Event-linked" mass accumulation rates (MARs) were derived from the CRS _PW model. In combination with the dry bulk density, organic matter content, ⁴⁰ K and ²¹⁰ Pb activity concentrations, these "event-linked" MARs were used for the identification of one or more event layers (turbidites, detrital layers) in 1-cm thick sediment samples. "Continuous" mean MARs which are independent of the event layers were estimated: in Lago Maggiore sediment cores they are 0.066-0.090 g cm ^-2 yr ^-1 ; in Lago di Lugano they vary in the range of 0.032-0.057 g cm ^-2 yr ^-1 with higher values in the time interval 1963-1986 as compared to 1986-present.
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